1. Field of the Invention
The present invention relates to a valve or valving system which may be used for switching between flowing gas streams without the undesirable interaction of the gas with any dead volume area or non-metallic surfaces.
2. Description of the Background
As the demand for integrated circuits having higher densities has increased, so also has the demand for process gases of ever increasing purity. In order to obtain such gases, it is necessary to use ultra-high purity gas distribution systems. In order to more fully understand the operation of the various components of an ultra-high purity gas distribution system, however, it is necessary to ascertain the effect of impurities on the gas distribution system components.
The gas distribution system components can be tested using an apparatus which is capable of rapidly switching between a high purity gas and a gas doped with a known quantity of impurity. In such a test, comparative information is obtained regarding the relative response of the various components of the gas distribution system to a disturbance or perturbation from a high purity environment. In more detail, a pulse of impurity is injected into a particular component to ascertain what, if any, interactions occur between the particular impurity and the internal surfaces and geometries of the test device.
Where the component being tested has a far greater surface interaction than the combination of switches or valves which may alternately be used, the relatively small contribution from the alternate switching or valve system may be neglected. However, where the component has a surface interaction which is not much greater than or is of approximately the same magnitude as the combination of valves which may alternately be used, the contribution from the alternate switching or valve system cannot be neglected.
Unfortunately, at present, no means exists for adequately determining which component is most desirable for a particular application, particularly in systems where a component of interest has a surface interaction which is not much greater than or is of approximately of the same magnitude as the combination of valves which may alternately be used.